The present invention relates generally to irrigation systems.
There has been used in the past so called "pop-up" irrigation units having a housing with an internal riser operated by water pressure within the housing to extend the riser upwardly, and thereafter operate a conventional irrigation sprayer. One such "pop-up" unit is manufactured by the Toro Company under U.S. Pat. Nos. 4,609,146 and 4,682,732. A similar "pop-up" system is sold by the Rainbird Company under U.S. Pat. Nos. 4,316,579 and 4,479,611.
In recent years, there has been increased interest in devising techniques for reducing the volume of water emitted from a conventional sprayer. To that end, they have been devised so called "low volume" emitter systems. One type of emitter system is sold by Thayer Industries, Inc. of Dundee, Florida under the trademark MAXIJET; these products generally consist of a base having a threaded downward extension and a bead across the top of the base, with a "snap on" emitter head having a fixed aperture.
In the past, the pop-up irrigation systems of the type described above have operated at internal pressures on the order of 40-60 pounds per square inch (p.s.i.). However, those pressure levels are not suitable for use with low volume irrigation systems of the MAXIJET-emitter variety tend to pop away from the base at pressures in excess of 25 p.s.i. Further, such low volume emitters tend to clog easily when operated at elevated pressures.